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Across
  1. 5. the last of the noble gases
  2. 7. the last element of the alkali metals
  3. 9. molecules that exist in pairs
  4. 11. the lightest element
  5. 13. the father of the periodic table
  6. 15. the first metalloid element
Down
  1. 1. a subatomic particle with no charge
  2. 2. one of the most common radioactive materials
  3. 3. a metallic element with the symbol of Fe
  4. 4. the last element as of today
  5. 6. the plum ___________ model was developed by
  6. 8. group 7A of the periodic table
  7. 10. nuclear power plants
  8. 11. the atomic symbol for mercury
  9. 12. exists properties of both metals and non-
  10. 14. the proponent of the name of the atom